That's not the kind of "free to play" that Valve promotes. The phone apps are much, much more spammy. Valve mostly takes AAA games and can open them for free because the money they make as a facilitator between content creators and consumers pays for the game. The content makers make awesome stuff and get paid, the consumers get awesome stuff and have fun. Valve takes a commission for providing both the entertainment and payment platform. Everyone wins.

It's a one-way street on most phone apps. The devs write a little phone game, and then put 90% of it behind staged paywalls. Quite a different thing than what Gabe has done, and what he discusses here.